Method and apparatus for manufacturing packaging bags, and bags obtained thereby

Abstract

The present invention relates to a method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the steps consisting in: forming respective cutouts ( 150, 160 ) in each of the two lateral, bellows-forming zones of a packaging bag sheet ( 100 ) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and heat-sealing ( 184, 186 ) the adjacent edges of the sheet to the peripheries of the cutouts ( 150, 160 ) to close the bag. The invention also provides apparatus for implementing the method and bags obtained thereby.

What is claimed is:  
     
       1. A machine for manufacturing packaging bags from packaging bag sheets, comprising: 
       means for feeding a packaging bag sheet having a longitudinal extent;  
       means for folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;  
       means for forming cutouts within each one of said pair of laterally spaced bellow regions of said packaging bag sheet so that said packaging bag has only two sheet thicknesses superimposed with respect to each other within a mouth region of said packaging bag, wherein each one of said cut-out portions is defined by two rectilinear longitudinal edges coinciding respectively with outer definition lines of said laterally spaced bellow regions, a first rectilinear transverse edge extending transversely with respect to said longitudinal extent of said packaging bag sheet, and a second non-rectilinear transverse edge that is concave towards said mouth region of said packaging bag; and  
       means for heat sealing together edge portions of said packaging bag sheet to edge portions of said cutouts so as to close and seal said packaging bag.  
     
     
       2. A machine according to  claim 1 , further comprising: 
       means for feeding said packaging bag sheet in a direction parallel to said longitudinal extent of said packaging bag sheet; and  
       means for forming said pair of laterally spaced bellow regions so as to comprise a pair of Z-folds which extend parallel to said longitudinal extent of said packaging bag sheet.  
     
     
       3. A machine according to  claim 2 , wherein: 
       said means for forming said pair of laterally spaced bellow regions comprising said pair of Z-folds comprises a pair of blades that are partially superimposed with respect to each other so as to partially overlap each other and thereby form a baffle into which said packaging bag sheet is engaged so as to form said pair of Z-folds.  
     
     
       4. A machine according to  claim 3 , further comprising: 
       a cut-out punch; and  
       one of said pair of fold-forming blades comprises an anvil for said cut-out punch when said cut-out punch is used to said cut-outs so as to leave one of the faces of said packaging bag sheet intact.  
     
     
       5. A machine according to  claim 1 , wherein: 
       said machine comprises a form, fill, and seal machine.  
     
     
       6. A machine according to  claim 5 , wherein said form, fill, and seal machine comprises: 
       a forming throat having an inlet for said packaging bag sheet in a substantially planar state, and an outlet for delivering said packaging bag sheet outwardly from said forming throat of said form, fill, and seal machine in the shape of a tube;  
       a filling chute which opens out into said forming throat and consequently into said tube so as to deposit material into said tube;  
       first longitudinal heat-sealing means for closing and sealing said tube longitudinally; and  
       second transverse heat-sealing means for sequentially generating transverse lines of heat-sealing so as to close and seal said tube transversely and thereby form said packaging bag.  
     
     
       7. A machine according to  claim 1 , further: 
       means for placing transversely oriented complementary male and female closure strips upon said packaging bag sheet within the vicinity of said mouth region of said packaging bag such that said closure strips extend transversely with respect to said longitudinal extent of said packaging bag sheet.  
     
     
       8. A machine according to  claim 7 , further comprising: 
       means for initially securing said closure strips in position upon said packaging bag sheet by spot heat-sealing end portions of said closure strips to said packaging bag sheet.  
     
     
       9. A machine according to  claim 2 , further comprising: 
       means for fixing said Z-folds by spot heat-sealing said Z-folds at zones wherein transverse lines of heat-sealing are formed so as to close and seal said packaging bag.  
     
     
       10. A machine according to  claim 9 , further comprising: 
       heat-sealing means for forming two mutually parallel transverse lines of heat-sealing wherein a first one of said two mutually paralel transverse lines of heat-sealing coincides with said first rectilinear transverse edge of each one of said cutouts so as to form the bottom of said packaging bag, while a second one of said two mutually parallel transverse lines of heat-sealing is formed between said first rectilinear and second non-rectilinear transverse edges of said cutouts so as to form said mouth of said packaging bag; and  
       heat-sealing means for forming additional heat-sealing lines along said longitudinal edges of said cutouts and along said second non-rectilinear transverse edges of said cutouts.  
     
     
       11. A machine according to  claim 10 , further comprising: 
       means for forming a rectilinear cut line between said two mutually parallel transverse lines of heat-sealing so as to facilitate separation of formed packaging bags into separate adjacent packaging bags.  
     
     
       12. A machine for manufacturing packaging bags from packaging bag sheets, comprising: 
       means for feeding a packaging bag sheet having a longitudinal extent;  
       means for folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;  
       means for forming cutouts within each one of said pair of laterally spaced bellow regions of said packaging bag sheet so that said packaging bag has only two sheet thicknesses superimposed with respect to each other within a mouth region of said packaging bag, wherein each one of said cut-out portions is defined by two rectilinear longitudinal edges which are respectively set back from outer definition lines of said laterally spaced bellow regions, a first rectilinear transverse edge extending transversely with respect to said longitudinal extent of said packaging bag sheet, and a second non-rectilinear transverse edge that is concave towards said mouth region of said packaging bag; and  
       means for heat sealing together edge portions of said packaging bag sheet to edge portions of said cutouts so as to close and seal said packaging bag .  
     
     
       13. A machine according to  claim 12 , further comprising: 
       means for feeding said packaging bag sheet in a direction parallel to said longitudinal extent of said packaging bag sheet; and  
       means for forming said pair of laterally spaced bellow regions so as to comprise a pair of Z-folds which extend parallel to said longitudinal extent of said packaging bag sheet.  
     
     
       14. A machine according to  claim 13 , wherein: 
       said means for forming said pair of laterally spaced bellow regions comprising said pair of Z-folds comprises a pair of blades that are partially superimposed with respect to each other so as to partially overlap each other and thereby form a baffle into which said packaging bag sheet is engaged so as to form said pair of Z-folds.  
     
     
       15. A machine according to  claim 14 , further comprising: 
       a cut-out punch; and  
       one of said pair of fold-forming blades comprises an anvil for said cut-out punch when said cut-out punch is used to said cut-outs so as to leave one of the faces of said packaging bag sheet intact.  
     
     
       16. A machine according to  claim 12 , wherein: 
       said machine comprises a form, fill, and seal machine.  
     
     
       17. A machine according to  claim 16 , wherein said form, fill, and seal machine comprises: 
       a forming throat having an inlet for said packaging bag sheet in a substantially planar state, and an outlet for delivering said packaging bag sheet outwardly from said forming throat of said form, fill, and seal machine in the shape of a tube;  
       a filling chute which opens out into said forming throat and consequently into said tube so as to deposit material into said tube;  
       first longitudinal heat-sealing means for closing and sealing said tube longitudinally; and  
       second transverse heat-sealing means for sequentially generating transverse lines of heat-sealing so as to close and seal said tube transversely and thereby form said packaging bag.  
     
     
       18. A machine according to  claim 12 , further: 
       means for placing transversely oriented complementary male and female closure strips upon said packaging bag sheet within the vicinity of said mouth region of said packaging bag such that said closure strips extend transversely with respect to said longitudinal extent of said packaging bag sheet.  
     
     
       19. A machine according to  claim 18 , further comprising: 
       means for initially securing said closure strips in position upon said packaging bag sheet by spot heat-sealing end portions of said closure strips to said packaging bag sheet.  
     
     
       20. A machine according to  claim 13 , further comprising: 
       means for fixing said Z-folds by spot heat-sealing said Z-folds at zones wherein transverse lines of heat-sealing are formed so as to close and seal said packaging bag.  
     
     
       21. A machine according to  claim 20 , further comprising: 
       heat-sealing means for forming two mutually parallel transverse lines of heat-sealing wherein a first one of said two mutually paralel transverse lines of heat-sealing coincides with said first rectilinear transverse edge of each one of said cutouts so as to form the bottom of said packaging bag, while a second one of said two mutually parallel transverse lines of heat-sealing is formed between said first rectilinear and second non-rectilinear transverse edges of said cutouts so as to form said mouth of said packaging bag; and  
       heat-sealing means for forming additional heat-sealing lines along said longitudinal edges of said cutouts and along said second non-rectilinear transverse edges of said cutouts.  
     
     
       22. A machine according to  claim 21 , further comprising: 
       means for forming a rectilinear cut line between said two mutually parallel transverse lines of heat-sealing so as to facilitate separation of formed packaging bags into separate adjacent packaging bags.